The present disclosure relates generally to communication systems, and more particularly, to demodulation reference signal (DM-RS) configuration in a multi-input multi-output (MIMO) wireless communications system.
Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources. Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.
These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example telecommunication standard is Long Term Evolution (LTE). LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by Third Generation Partnership Project (3GPP). LTE is designed to support mobile broadband access through improved spectral efficiency, lowered costs, and improved services using OFDMA on the downlink, SC-FDMA on the uplink, and MIMO antenna technology. However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE technology. These improvements may also be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.
In wireless communication systems, a plurality of user equipments (UEs) served by a particular eNodeB may receive configuration data from the eNodeB for configuration of uplink communication. For example, the eNodeB may assign resources to multiple UEs to support MIMO communication and transmission of reference signals by each UE. However, a UE in MIMO communication may not be able to communicate reference signals useful for channel estimation and decoding of uplink data by the eNodeB if such reference signals (e.g., legacy reference signals) are communicated in only one symbol of a transmit time interval (TTI) of the UE. As such, improvements in the communication of reference signals by one or more UEs in a wireless communications system are desired.